This invention relates to an impact resistant panel composed of a group of at least three sheets of vitreous material bonded together via intervening layers of plastic material.
The term "vitreous material" as here used comprehends glasses and vitrocrystalline materials, the latter being glasses which have been treated in such a way as to cause the formation of one or more crystalline phases therein.
Such panels are resistant to the impact of stones, bullets and other similar projectiles. Such panels are therefore often used to form part of a bulletproof screen in banks and post offices, or to form windows, especially windshields, of aircraft and high speed locomotives. The panels are also resistant to breakage by vandals and may be used in display cases in museums, or to provide transparent barriers in prisons.
Hitherto, such panels have needed to be very thick in order to provide adequate impact resistance.
This has resulted in a very heavy and therefore expensive panel. Heavy panels suffer from the further disadvantage that they require heavy supporting structures or frames, and heavy panels are clearly unsuitable for use in aircraft.